The forced water-oil displacement in capillary is a model that has important applications such as the groundwater remediation and the oil recovery. Whereas it is difficult for experimental studies to observe the displacement process in a capillary at nanoscale, the computational simulation is a unique approach in this regard. In the present work, the many-body dissipative particle dynamics (MDPD) method is employed to simulate the process of water-oil displacement in capillary with external force applied by a piston. As the property of all interfaces involved in this system can be manipulated independently, the dynamic displacement process is studied systematically under various conditions of distinct wettability of water in capillary and miscibility between water and oil as well as of different external forces. By analyzing the dependence of the starting force on the properties of water/capillary and water/oil interfaces, we find that there exist two different modes of the water-oil displacement. In the case of stronger water-oil interaction, the water particles cannot displace those oil particles sticking to the capillary wall, leaving a low oil recovery efficiency. To minimize the residual oil content in capillary, enhancing the wettability of water and reducing the external force will be beneficial. This simulation study provides microscopic insights into the water-oil displacement process in capillary and guiding information for relevant applications.

Background This study aims to analyze the effect of the body mass index (BMI) on E2, P and LH values in females who received intrauterine insemination (IUI) treatment on human chorionic gonadotropin (HCG) day. Methods A total of 2319 cycles of IUI-assisted pregnancy treatment were selected in our hospital. Based on the BMI, female infertility patients are divided into three groups: normal weight group, overweight and obese group. Results For patients with natural cycles and ≤ 35 years old, there were 440, 178 and 197 cases in the three groups, respectively. For patients with natural cycles and > 35 years old, there were 90, 83 and 81 cycles in the three groups, respectively. For patients with induced ovulation cycle and ≤ 35 years old, there were 425, 203 and 516 cases in the three groups, respectively. For patients with induced ovulation cycle and > 35 years old, there were 26, 26 and 54 cases in the three groups, respectively. Conclusion When a patient is ≤35 years old, the BMI affects the E2, LH and P values on the day of artificial insemination. However, the BMI is negatively correlated with E2, LH and P in IUI on HCG day. After controlling for age and assisted pregnancy, the correlation analysis revealed that the BMI is negatively correlated with hormone E2 and LH. The higher the BMI was, the lower the levels of hormones E2, LH and P became. However, in the present study, the BMI did not significantly improve the clinical pregnancy rate of patients who received IUI.

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